Beam-control semiconductor oscillator

ABSTRACT

An electron beam high frequency generator and circuit arrangement in which a pencil of electrons (i.e., an electron beam) is trained at an acute angle against an elongated semiconductor bar in series with a current source and an electrode. A pair of deflector plates flank the beam to provide static or varying spreading of the latter while a grid permits control of the beam current and, therefore, the frequency of the device. By applying varying potential to the deflector plates, a modulation is superimposed upon the carrier frequency.

United States Patent [72] Inventor Kiyoshi lnoue 100 Sakato, Kawasaki,Kanagawa, Tokyo, Japan [21 Appl. No. 603,971 [22] Filed Dec. 22, 1966[45] Patented Sept. 28, 1971 {32] Priority May 12, 1966, June 11, 1966[3 3] Japan [31] 41/30181 and41/37634 [54] BEAM-CONTROL SEMICONDUCTOROSCILLATOR 5 Claims, 10 Drawing Figs. [52] 0.8. CI 332/25, 331/107 R,313/65 AB, 332/16, 313/64, 313/311 [51] Int. Cl ..H01j 31/58, 1103c3/34, 1103b 5/12 [50] Field of Search 313/89, 65 A; 330/33; 315/31;331/107, 107 G; 332/25 [56] References Cited UNITED STATES PATENTS2,540,490 2/ 1951 Rittner 330/33 2,588,292 3/1952 Rittner et a1 313/89 X2,589,704 3/1952 Kirpatrick et a]... 313/89 X 3,344,300 9/1967 Lehrer eta1. 313/89 X 2,678,400 5/1954 McKay 313/68 3,144,575 8/1964 Babits....313/65 A 3,230,473 1/1966 Adler 330/4.7 X

Primary Examiner-Robert Sega] Attorney-Karl F. Ross ABSTRACT: Anelectron beam high frequency generator and circuit arrangement in whicha pencil of electrons (i.e., an electron beam) is trained at an acuteangle against an elongated semiconductor bar in series with a currentsource and an electrode. A pair of deflector plates flank the beam toprovide static or varying spreading of the latter while a grid permitscontrol of the beam current and, therefore, the frequency of the device.By applying varying potential to the deflector plates, a modulation issuperimposed upon the carrier frequency.

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FIG. 6

KIYOSHI INOUE INVI'IN'IUR,

Y W Attorney PATENTED SEP28 l97l SHEET 4 0F 4 K A w Attorney FIG.7B

, i BEAM-CONTROL SEMICONDUCTOR OSCILLATOR My present invention relatesto a beam-control electronic device, and, more particularly, to a highcurrent vacuum tube suitable for use in switching, amplifying,electronic display, or the like.

Beam-type vacuum tubes of conventional character can be divided into twocategories, namely amplifying arrangements and display devices. In anamplifying system of the usual type, a thermionic emitter is energizeddirectly or indirectly to produce electrons which drift from a cathodeto an anode, e.g. the plate of the vacuum tube, under the interveningcontrol of one or more grids maintained at various potentials so as toregulate the current-carrying capacity of the electron cloud or stream.in practice, therefore, the amplification characteristics are determinedby the density of the electron cloud and, of course, the currentrepresented thereby. The application of relatively small potentials andelectric currents to the control grids permits a relatively small amountof energy (the grid-dissipation power) to regulate a comparatively largeamplitude (e.g. the current-carrying capacity to the electron beam).Devices of this type are prone to malfunction because of thermalconsiderations and have current-carrying capacities which are limited bytechnical considerations in this respect. In fact, the amount of heatgenerated at the anode or plate by kinetic impact of the impinging beamthereon is directly related to the current carried by the beam so thatheat sinks, gas or liquid cooling means and the like must be providedfor the higher power tubes. Even with such expedients, difficulties areencountered since higher energy and amplitude electron beams producemechanical erosion with deterioration of the grids, the cathode and theanode.

In display-type devices, such as cathode-ray tubes, the electron beamdoes not necessarily impinge upon a plate, so that the kinetic energy ofthe beam is dissipated at this anode, but is projected against afluorescent surface which is energized by the beam and creates visiblelight. In this case, the usual control grids are provided to switch thebeam on and off while regulating the amplitude (beam current) of thebeam and the illumination produced thereby. Acceleration of the electroncloud is effected by anodes forwardly of the grids and orientation ofthe beam is determined by deflecting plates, In such beam devices, it isalso a common practice to use magnetic fields to focus, concentrate,deflect or disperse the beam and, indeed, magnetic lenses of varioustypes are available for this purpose.

In all such systems, the controlled current is in effect the beamcurrent and thus the electron current passing through the tube. Whilerelatively higher grid currents are necessary to regulate the principalcurrent flow, this latter is limited by mechanical considerations.

It is therefore the principal object of the present invention to.provide a beam-controlled electron tube in which the controlled currentis not limited by the electron current of the beam, which has a longerlife than conventional tubes with control of correspondingly largercurrent flows, and has greater flexibility than conventional beam-powertubes.

Another object of this invention is to provide a high response, highcurrent vacuum tube having a relatively high impedance at the controlelement such that larger currents can be regulated with low controlpower.

Still another object of this invention is to provide a system forcontrolling the power supply of an electrochemical machining or electricdischarge machining process with greater accuracy and efficiency thanhas been possible heretofore.

Still another object of my invention is to provide a display tube withbetter control than has been possible with conventional cathode-raysystems.

These objects and others which will become apparent hereinafter areattained, in accordance with the present invention, with a vacuum-tubesystem in which an electron beam acts as the control element of asolid-state three-element switching device. Thus, if the solid-stateswitching system can be considered to be the equivalent of a transistorof high current-carrying and switching capacity, the solid junction orsandwich-type control layer being sensitive to photon energization, aelectron beam is directed against the solid-state body such that itregulates the current flow characteristics between the collector andemitter (if the system is of transistor type), between the anode and thecathode (e.g. if the system is of the controlled-rectifier type), orbetween the terminals of a resistance element (e.g. when the system isof the photoresistive or photoconductive type).

In practice, the solid-state element will have at least two terminalsand a resistivity characteristic modifiable by the impinging electronbeam and will be disposed in the path of such a beam which may begenerated by a conventional electron gun or other thermionic source.According to this invention the electron gun is itself provided with oneor more control grids and/or high voltage beam-deflection means forregulating the intensity of the electron beam or its orientation andthereby controlling the conductivity characteristics of the solid-statedevice. Since a relatively low beam current can serve to switchcomparatively large solid-state currents, the thermal dissipation of thevacuum tube will be much less than the dissipation required inbeam-power tubes in which the full controlled current appears as theelectron current flow. Furthennore, a still smaller energy is necessaryat the grid or deflection plate since the very nature of the beam is oneinvolving amplification of whatever parameter has been applied thereto.Thus, the control grid of the electron gun can have an extremely highimpedance input and require very meager control power by comparison withthe beams and energy necessary for conventional beam-power tubes.

According to another aspect of the present invention, the electronicdevice is used to generate a high frequency pulse or a periodicfluctuating output by repetitively sweeping an electron beam against alongitudinally extending solid-state element energized with directcurrent. If this elongated element is connected at terminals at itsopposite ends with a DC source and a load, the electron beam sweepingalong this element from one side to the other will cause, in effect, anelectron drift (i.e. of excess electrons) in the direction of the sweepof the beam or will progressively cancel electron depletion of thesemiconductor as it sweeps thereacross. As a consequence, the loadcurrent will appear as a series of pulsations at the cadence of thesweep of the beam. By properly timing and controlling the beam-sweeprate, the generator can be used effectively as a variable-frequencyoscillator of substantially any output with considerable insensitivityto transients, since neither the time-control elements, nor thesolid-state device are hypersensitive thereto. Since thecurrent-carrying capacity of the solid-state device is only a functionof the characteristic of the semiconductive material employed, theoscillator can control relatively high powers without difilculty.Moreover solid-state control of high frequency signals is possible.

Another feature of this invention resides in the provision of avariable-frequency oscillator using a semiconductor in the mannergenerally described above. I have discovered, in accordance with thisaspect of the invention, that a continuous electron beam directedagainst an elongated semiconductor body at an acute angle will cause thestate of the body to switch periodically at high frequency between aconductive state and a nonconductive state. Thus, when the semiconductoris connected in series with a source of electric current and a load, ahigh frequency current will'be applied to the latter at a frequencydetermined by the beam current impinging upon the semiconductor.

According to yet another aspect of this invention, theelectron-beam-controlled conductivity of a semiconductive substance isused to intensify the image displayed upon a television screen. Thephosphors used upon the screen, in this case, are not only energized bythe electron beam but are intensified in their fluorescent output by anelectroluminescent effect. For this purpose, the phosphor is laminatedto the semiconductive layer between a pair of electrodes anda source ofdirect current or pulsating current connected across the laminate.Normally, the semiconductor is in a nonconductive state and noemission-intensifying current passes through the phosphor. when,however, the phosphor is activated by the electron beam at a particularregion of the screen, the translumination of the immediately adjoiningsemiconductor material renders this region of the switching layerconductive so that an electroluminescent intensification of the emissionresults from the passage of current through the semiconductor orphosphor layers.

The above and other objects, features and advantages of the presentinvention will become more readily apparent from the followingdescription, reference being made to the accompanying drawing in which:

FIG. l is a diagram of a beam-control tube in accordance with thepresent invention;

FIG. 2 is a graph showing some of the characteristics of this tube;

MG. 3 is a circuit diagram of a system for the electricdischargemachining of a workpiece and using an electronbeam tube of the presentinvention;

FIG. 8 is a diagram of another tube arrangement embodying theseprinciples;

FIG. 5 is a diagram of a high frequency generator using an electron beamas the control means;

FIGS. 5A and 5B are graphs showing characteristics of the tube of FIG.5;

FIG. 6 is a view similar to FIG. 5 of another embodiment of thisinvention;

FIG. 7A is a diagram of a cathode-ray television tube for the display ofcolor images according to this invention; and

FIG. 7B is a cross section of the face of this tube drawn to an enlargedscale and illustrating certain principles of the inventron.

In FIG. 1 I show an amplifier-type beam-power tube which is hereillustrated in diagrammatic form. The evacuated tube 10 has a filamentor heater 11 which serves to raise a thermionic-emission cathode 12 to atemperature sufficient to cause the latter to emit electrons. juxtaposedwith cathode 12 on the opposite side of an electron-drift space 13, Iprovide an anode 14 in the form of a plate of semiconductive material towhich a pair of terminals are spacedly fused at 15 and 16. In effect,therefore, the terminals 15 and 16 can be considered equivalent to theemitter and collector of a transistor or to the anode and cathode of asolid-state controlled rectifier switch in which the plate 14- controlsflow of current through the junctions of the terminals and the plateand, therefore, between the electrodes. If the photon-activatablesemiconductive body 14 is only a photoresistive material, the terminals15 and I6 are interchangeable in function and can be connected in serieswith any load (e.g. as shown at 15') to be controlled by varying theresistivity of the semiconductor device 14-16.

Between the cathode 12 and the semiconductive plate 14 of the vacuumtube, I provide the usual control grid 17 and, as is common inbeam-power tubes, a screen grid 18. While an electron-acceleratingcircuit may be provided at B to promote the electron flow between acathode and an anode, it will be understood that the screen grid 18,which has been provided with a relatively positive potential bycomparison with the cathode, can also have an accelerating function.

Input is through the control grid 17 as represented at I, thecontrolgrid being maintained at a potential below the potential of thecathode in the usual manner. Thus when the grid 17 is so poled as toprevent electron drift in the direction of the plate 14, thesemiconductive device 14-16 can be totally nonconductive or cut off toprevent any current flow between the terminals 15 and 16.

In FIG. 2, I show the characteristics of such a system using a cadmiumsulfide semiconductive plate 14, a plate voltage from battery B of 600volts and an output as represented along the ordinate. Along theabscissa, I have plotted the beam current in microamperes. Thus it canbe seen that a current flow between the terminals 15, 16 of 0-500milliamps (0 to 0.5 a.)

can be controlled with a beam current ranging between 0.01 and 0.07microamperes and a fraction of this current at the grid. I-leatdissipation is no longer a problem while a reduced dimensioning of theentire system is possible.

EXAMPLE I Using a tube of the type illustrated in FIG. 1 with a platevoltage of 600 volts, a cadmium sulfide anode 14 as the plate, a controlgrid and a screen grid as illustrated in FIG. 1, the plate resistancewas found to be variable between 2,000 ohms and 24 ohms. With the aid ofthe control grid 17, the beam or electron current between cathode l2 andplate 14 was varied from 0.01 to 0.07 microamperes to yield outputsthrough the plate 14 as shown along the ordinate of FIG. 2. Similarresults were obtained when the cadmium sulfide plate 14 was replaced bysemiconductive materials from the following group: silicon, germanium,gallium arsenide, silicon carbide, cuprous oxide, zinc sulfide, leadtritelluride, lead sulfide, indium phosphite, aluminum antimonide andindium antimonide.

It will be understood, of course, that the beam-power tube of FIG. 1 canbe used in substantially any semiconductive circuit with a degree ofamplification selected by modifying the plate voltage and the inputsignal applied to the control grid 17.

In FIG. 3, I show an electron-beam tube as incorporated in an apparatusfor regulating the power of an electric discharge machining (EDM)system. It will be understood that the system is also applicablewhenever control of relatively high current pulses is required with atriggering system of low capacity designed to feed into a high impedancecontrolling device.

In the system of FIG. 3, the beam-power tube is evacuated and contains aheater 11] across which an A battery 121 is connected to represent anysource of heater current. This heater or filament raises the temperatureof a thermionicemitting cathode 112 which is connected to the negativeterminal of the plate supply 5" battery 122 whose positive terminal isconnected via a balancing potentiometer 123 to a pair of deflectingplates 124, 125 which are normally at precisely the same potential so asto ensure undeflected passage of the electron beam. The plates 124, 125here act as accelerating anodes for the electron beam which, because ofits high velocity and kinetic energy, impinges upon a semiconductiveelectron-activatable body 114 whose terminals 115 and 116 are connectedin series with the power supply for an electricdischarge machiningapparatus 126. A focusing shield 127 is provided adjacent the cathode112 and is maintained at a positive potential somewhat above that of thecathode by a battery 128. The tube 110 also is formed with a controlgrid 117 which serves to switch the electron beam under the control of atriggering device 130 which may have a very high output impedance and beof low power. The triggering device is here constituted as a transistormultivibrator whose PNP transistors 131, 131 are connected in the usualfree-running multivibrator network with a pair of RC networks 132determining the pulse frequency and duration. The multivibrator 130 hasa supply voltage source such as a battery 133. The transistor 131' thusacts as an amplifier and has its emitter-collector terminals in serieswith a biasing C battery 129 and the control grid 117. The battery 129is returned to the cathode.

The semiconductive variable-resistance block or plate 114, which isdisposed in the path of the electron beam or cloud, is connected inseries with the EDM power supply represented as a battery the electrodesystem, here illustrated diagrammatically, is a machining electrode 141and a vessel 142 retaining the dielectric medium and serving as asupport for the workpiece.

A pulse-shaping resonating network of inductances 143 and capacitances144 is connected across the EDM machining system 141, 142 in order topromote the development of electric discharges thereacross. When theelectron beam of tube 110 is pulsed by the application of electricpulses at high frequency to the grid 117 by the multivibrator 130, thesemiconductor 114 is rendered operative and closes a circuit through thebattery 140 and the machining gap formed between the electrode 141 andthe workpiece. Current surges from capacitors 144 are superimposed uponthe discharge produced by the instantaneous conductivity of thesemiconductor 114. I have found that with a cadmium sulfide plate 114having a thickness of 2 mm. and using a control current of microamperesto I00 microamperes at the grid 117 it is possible to control a currentflow in the EDM circuit of 250 amperes at 50 volts of the source 140.Accurate control is provided even at frequencies greater than 55kilocycles/sec.

A feedback regulation of the power can be supplied by another grid 118which is biased by a feedback amplifier and sensor 145.

The arrangement illustrated in FIG. 4 represents a modified tube foroperating in sequence a multiplicity of EDM, ECM or other materialremoval systems or for generating pulsing currents therefore. The tubeof FIG. 4 comprises an evacuated envelope 210 whose cathode 212 isheated by a filament 211 and is part of an electron gun including afocusing plate 227, a control grid 217, a feedback grid 218 and a pairof deflector plates 224 and 225 respectively flanking the electron beamor pencil which is represented by the dot dash line 246.

In this system, the semiconductive plate 214 is subdivided into aplurality of zones 214a, 2l4b and 214c in a direction transverse to thebeam in which the beam may be deflected by electrostatic potentialsapplied to the plates 224 and 225. A common electrode 214d is providedfor all the sections 214a-2140 and consists of a vapor-deposited metalfoil substantially transparent to electron irradiation. This conductivelayer 214d can be connected with the B+ terminal of the battery 222(whose B-terminal is connected with the cathode 212) as well as with oneside of the machining source 240. Each of the sections 2140, 214k and2140 can be connected with a respective electrode similar to that shownat 141 in FIG. 3 of a respective machining arrangement or to therespective portion of a single electrode. The other side of battery 240is, of course, connected to the other terminal of the machining system.It will be apparent, therefore, that when the electron pencil or beam246 is deflected laterally (arrow 247) by the application of suitablepolarities to the deflector plates 224 and 225, the beam 246 will sweepsuccessively or alternately into impinging relationship with each of thesemiconductive sections 214a-214v which are electrically insulated fromone another. These sections will be rendered conductive in turn.

When, for example, an alternating current is applied across thedeflector plates 224, 225 from the sweep-voltage source 230, athree-mode operation can be discerned. In the first mode, the plate 224is relatively positive and the plate 225 relatively negative during partof each cycle such that the beam 246 is deflected to impinge upon thesection 214a and render the latter conductive. The machining electrodeconnected with this section is then triggered as described withreference to FIG. 3. During the opposite portion of the cycle thedeflecting plate 224 is relatively negative and plate 225 relativelypositive whereupon the beam impinges upon the section 2140 to energizeits electrode or electrode portion. During the intervening period, thebeam 246 sweeps across the section 214b and energizes its electrode orelectrode portion. Thus if all three sections 214a-2140 are connected toa single electrode, three pulses will be delivered of amplifying currentfor each cycle of the control current supplied to the deflecting plates224.

The magnitude of the current flowing to the machining system will dependupon the bias at the grid as previously indicated. The triggering source230 can, however, be pulsed to alternately energize the deflector plates224, 225 so that, in the unenergized position of the plates, the beamimpinges upon section 2141: whereas alternate energization of the plates224. 225 causes deflection of the beam 246 to the-corresponding sidewith energization of the sections 214a and 214b for the duration of theenergizing pulse.

In FIG. 5, I show a modified beam-tube system according to the presentinvention wherein the evacuated envelope 310 encloses an electron gunconsisting of a filament or heater 31 1, a cathode 312 adapted to bebrought to thermionic emission temperature by the heater, a control grid317 in the path of the electron beam (diagrammatically represented byits axis 346), and an anode formed by a pair of deflecting plates 324and 325. The heater 311 is connected to the usual A" battery 321 while a8" battery or other source 328 has its negative terminal tied to thecathode 312 while its positive terminal is connected via the wiper of abalancing potentiometer 323 to the deflecting electrodes 324 and 325.The level of the positive potential at these deflecting electrodes canbe set by adjustment of the potentiometer 323 so that the spread of theelectron beam 346 can be controlled and the beam caused to impinge at anacute angle upon a semiconductor body 314. The latter may be composed ofcadmium sulfide and may have a length of, say, 20 mm., a width of 1 mm.and a thickness of about 0.5 mm. so as to constitute a bar ofphotoconductive material in the plane of the axis of the beam.

The terminals 315 and 316 of the semiconductor bar 314 are joined toplates 315a and 316a printed onto the semiconductor or otherwiseretained as electrodes thereon. The terminals are connected in a loadcircuit including a source of electric current, such as the battery 340,and a resistance 341 representing any load requiring a high frequencyinput. The electron beam 346 is trained at an acute angle a, of 30 to a,of 12 as shown in FIG. 5) to the semiconductor bar 314, it has beenfound that the impingement of a high energy electron beam at an acuteangle upon a P-type, N-type or an impuritytype semiconductor will inducean oscillation of the current carriers within the layer and thusconstitute of the semiconductor a high frequency generator. As can beseen in FIG. 5, the beam includes the acute angle with the bar in thedirection of impingement of the beam.

The frequency of the generator can be controlled by varying parametersof the electron beam, namely, its energy and velocity and the number ofparticles, with the aid of the control grid and the plate voltage. ThusI have discovered that the high frequency output across the load 341varies in frequency with the plate current of the system and with thenumber of electrons constituting the beam.

EXAMPLE II In FIG. 5A, I show a graph in which the high frequency outputacross the load 341, in kilocycles per second, is plotted as theordinate against the plate current in microamperes (plotted as theabscissa). The curve was obtained with a plate voltage of 200 VDC usinga cadmium-sulfide semiconductor with the dimensions given earlier. Itcan be seen, therefore, that the output frequency of the system varieswith the beam current and thus the number of electrons permitted by thegrid 317 to pass. With the aid of conventional circuitry for modifyingthe grid potential, the system can be used to selectively generate awide range of frequencies. In FIG. 58, I have plotted the output currentin milliamperes (at 500 kilocycles per second for purposes of example)as the ordinate against the plate voltage as the abscissa. From thisgraph, it is apparent that the output power, as well as the outputfrequency, can be selectively adjusted within a wide range.

In FIG. 6, there is illustrated a modified oscillator system accordingto the present invention, which embodies principles described inconnection with FIGS. 4 and 5. In this system, the evacuated envelope410 again provides an electron gun training a beam 446 of electrons uponthe semiconductive bar of plate 414. The electron gun includes theheater or filament 411, a cathode 412, a control grid 417 and an anodeformed by a pair of deflection plates 424 and 425 flanking the beam 446.The electron-responsive semiconductor 414 is connected in circuit with abattery 440 and the load 441. As illustrated in FIG. 6, however, an ACsource 430 of low power but adjustable frequency is inductivelyconnected at 4300 in circuit with the plate source 428 and thedeflecting plates 424 and 425.

Thus, in addition to the natural oscillation of the current-carryingmeans of the semiconductor 414, as described in connection with FIG. 5,the electron beam 446 is spread and contrasted in the direction of arrow447 across the length of the semiconductor to superirnpose upon thenatural frequency determined by the plate current and beam power, amodulating alternating current determined by the oscillation frequencyof the source 430.

The present invention also is applicable to cathode-ray tubes of thedisplay type, for analog-to-digital conversion, or the like. In ananalog-to-digital conversion, the analog parameter is used to deflectthe beam (e.g. as indicated in FIG. 4) and thus sweeps it across aplurality of semiconductors, thereby providing an output at each of themcapable of digital process. In the improved system of the presentinvention, an amplified current flow is provided when the semiconductivebodies are connected in series with the battery or other source and anamplified pulse is obtained upon energization.

It is possible, moreover, to obtain a light amplification using similartechniques as illustrated in FIGS. 7A and 7B. In FIGS. 7A and 7B, 1 showa cathode-ray television picture tube for the display of color images,As is conventional, the picture tube comprises an evacuated glassenvelope 510 having a screen 514 at its forward end. A magneticdeflecting yoke is represented at 550 and is disposed forwardly of thethree electron guns adapted to respond to primary colors (e.g. red,blue, green and yellow). Each electron gun includes a respectivefilament or heater 511, a cathode 512, a control grid 517 representativeof the several grids normally provided in such systems, the plate 527and the usual focusing and sweep deflectors 524a and 524k disposed inpairs flanking the respective electron beams. The anodes 524a, ofcourse, represent the vertical-sweep electrodes while plates 5241;represent the horizontal sweep electrodes. Insofar as the aforedescribedstructure is concerned it is conventional and need not be discussedfully. The color kinescope tube has a phosphor dot screen upon the innersurface of its face plate, the screen 514 being of a laminatedconstruction. Thus, as can be seen in FIG. 78, a vapor-depositedelectrode layer 515a of aluminum, tin, copper or silver (transparent toelectron irradiation) is provided inwardly of an electron-activatablesemiconductor layer 514a of cadmium sulfide, zinc oxide or zinc cadmiumsulfide.

A further layer 551 of the conventional phosphor then underlies thesemiconductive layer 514a while a final electrode layer 5160(transparent to visible light) forms the final electrode of the laminateadjacent the faceplate 552 of the picture tube 510.

A DC source 540 is connected in series with a high frequency alternatingcurrent source 540a between the terminals 515 and 516 respectivelyconnected with the electrode layers 515a-516a. In this system, theelectron-activatable material 514a (which may not respond to X-rays orphotons) or photons acts as an electronic switch energized by theelectron beam to increase or decrease the current flow through anenergized portion of the phosphor 551 which is electroluminescent and,therefore, glows with the desired color and an intensity augmented bythe electric energizing current from sources 540 and 5400. Thus, bycontrast with conventional color tubes for television display, whichproduce images of an intensity directly related to the energy of theelectron beam and photon or X-ray image intensifiers and also requiringhigh beam currents and accelerating voltages, the present invention canmake use of only limited beam currents and obtain an intensivephosphorescence by the electroluminescent efiect controlled by thesemiconductive layer 514 a. In this respect, therefore, the layer 514aserves as a control device regulating the current flow through a load(the electroluminescently intensifiable phosphor 551) and controlled inturn, by the electron beam which serves the double purpose of energizingthe phosphor and triggering the semiconductor switching device.

EXAMPLE III In practice, the system of H68. 7A and 78 has been found tobe operative when the outer layer 515a of conductive materialtransparent to the electron beam has a thickness of about 200 angstromunits and is composed of aluminum, copper, silver or tin, when thesemiconductive layer 5140 of cadmium sulfide, zinc oxide or zinc cadmiumsulfide has a thickness of 10 microns, when the phosphor layer 551consists of one or more of the phosphors of the following table (withthe doping substance indicated with the color) for the respective colorsand having a thickness of about 10 microns, when the vapor-depositedelectrode layer 5160 is composed of aluminum, copper, silver or tin andhas a thickness of 200 angstroms, and when the sources 540 and 540a havea voltage and a frequency of volts and l kilocycle per secondrespectively.

The invention described and illustrated is believed to admit of manymodifications within the ability of persons skilled in the art, all suchmodifications being considered within the spirit and scope of theappended claims.

I claim:

1. An electronic device comprising an envacuated envelope; an elongatedsemiconductor member in the path of said beams, said member beingcomposed of an electron-activatable material of a degree of conductivityvariable in dependence upon the intensity of a stream of electronsimpinging thereon; an electron gun in said envelope trained permanentlyon said member for projecting thereupon an electron beam always at anacute angle with a surface of said member in the direction in which saidbeam is projected thereagainst; deflector means for spreading said beambetween said gun and said surface while maintaining the axis of the beamcontinuously inclined to said surface at an acute angle; and means forconnecting said semiconductor member at its ends in circuit with asource of electric current for energization of a load said meansincluding terminals affixed to said member at locations spacedtherealong in the direction of impingement of said beam whereby saidmember switches between relatively conductive and relativelynonconductive states at a high frequency determined by said intensity.

2. The device defined in claim 1 wherein said axis and said member aregenerally coplanar and said electron gun includes a thermionicallyemissive cathode, and a control grid forwardly of said cathode in thepath of said beam, said device further comprising control meansconnected to said grid for varying said intensity.

3. The device defined in claim 1 wherein said deflector means comprisesa pair of deflecting electrodes of variable electrical polarity forspreading said beam prior to its impingement upon said member.

4. An electric circuit including the electronic device of claim 1wherein said member is a semiconductor bar and said electron gunincludes a thermionically emissive cathode for generating said beam, atleast one control grid in the path of said beam for varying selectivelythe beam current, and means along the path of said beam for acceleratingthe electrons thereof toward said semiconductor member, said circuitincluding means connecting said source of electric current and said loadin series with said semiconductor member.

1. An electronic device comprising an envacuated envelope; an elongatedsemiconductor member in the path of said beam, said member beingcomposed of an electron-activatable material of a degree of conductivityvariable in dependence upon the intensity of a stream of electronsimpinging thereon; an electron gun in said envelope trained permanentlyon said member for projecting thereupon an electron beam always at anacute angle with a surface of said member in the direction in which saidbeam is projected thereagainst; deflector means for spreading said beambetween said gun and said surface while maintaining the axis of the beamcontinuously inclined to said surface at an acute angle; and means forconnecting said semiconductor member at its ends in circuit with asource of electric current for energization of a load said meansincluding terminals affixed to said member at locations spacedtherealong in the direction of impingement of said beam whereby saidmember switches between relatively conductive and relativelynonconductive states at a high frequency determined by said intensity.2. The device defined in claim 1 wherein said axis and said member aregenerally coplanar and said electron gun includes a thermionicallyemissive cathode, and a control grid forwardly of said cathode in thepath of said beam, said device further comprising control meansconnected to said grid for varying said intensity.
 3. The device definedin claim 1 wherein said deflector means comprises a pair of deflectingelectrodes of variable electrical polarity for spreading said beam priorto its impingement upon said member.
 4. An electric circuit includingthe electronic device of claim 1 wherein said member is a semiconductorbar and said electron gun includes a thermionically emissive cathode forgenerating said beam, at least one control grid in the path of said beamfor varying selectively the beam current, and means along the path ofsaid beam for accelerating the electrons thereof toward saidsemiconductor member, said circuit including means connecting saidsource of electric current and said load in series with saidsemiconductor member.
 5. The electric circuit defined in claim 1,further comprising means for varying the electrical potential of saiddeflector means for applying a modulation to the frequency determined bysaid intensity of said beam.